Abstract Diversity on science teams has been shown to increase research productivity and creativity yet the scientific workforce lacks sufficient diversity. A range of approaches to diversifying the workforce have been initiated, such as the BUILD and NRMN efforts, however we still lack scientific evidence as to which approaches work most effectively, with whom, and for what duration. Going forward, we need both new methods for diversifying the workforce and better ways to assess their effectiveness. This study seeks to test an intervention (Career Education and Enhancement for research Diversity (CEED)) designed for postdocs and junior faculty who are underrepresented in health-related sciences on a national basis. CEED aims to improve the Psychological Capital of underrepresented trainees by increasing their hope, efficacy, resilience, and optimism. These skills have repeatedly been shown to impact attitudes and performance. We propose a cluster randomized controlled trial to test the CEED intervention with 26 institutions. We will standardize the intervention so that it can be implemented consistently across the treatment sites. Near-peer mentors at the treatment sites will receive career coaching and mentor training so that they can deliver the intervention more effectively. We will follow participants for two years to study the impact of CEED. We will also study the factors that contribute to the participants success by engaging in qualitative research using participant interviews. Finally, when the trial is concluded, we will disseminate the intervention to the wait- list controls as well as other institutions for a broad dissemination. Our work aims to improve the culture for postdocs, fellows, and junior faculty who are underrepresented (UR) in the biomedical research workforce using near-peer and peer mentoring with a 12-month program that has been successful at retaining UR in academia and in research careers. By training near- peer mentors to offer the intervention, we empower them as role models. Additionally, by testing the effects of CEED on Psychological Capital through a rigorous experimental design, we will be able to identify a potential mechanism through which CEED works.